Enhancing interfacial adhesion of carbon fiber/poly(phthalazinone ether ketone) composites by the hybrid sizing agent of hydroxyapatite‐reinforced PAEK‐COOH

Abstract Improving the interfacial adhesion of carbon fiber (CF)/polymer composite is an urgent demand to enhance its mechanical properties. A kind of poly(aryl ether ketone) with carboxyl groups (PAEK‐COOH) was newly synthesized. PAEK‐COOH is similar to the thermal properties of PPEK matrix. Hydroxyapatite (HAp) was easily dispersed in an NMP solution containing PAEK‐COOH. Different kinds of hybrid sizing agents were obtained for preparing the prepreg through the solution impregnation. The hot‐pressing method was employed to produce the laminated composites. Flexural strength, flexural modulus and interlamellar shear strength (ILSS) of 0HP@CF/PPEK composites were improved by 8.8%, 17.3%, and 14.7%, respectively, in comparison to desized CF/PPEK. The interface bonding between CF and PPEK was improved by the addition of PAEK‐COOH sizing agent. Meanwhile, compared with desized CF/PPEK laminates, flexural strength, flexural modulus and ILSS of 5HP@CF/PPEK composites were enhanced by 63.5%, 87.4%, and 40.9%, respectively. The crack propagation path became dispersed and the stress was effectively absorbed when the sizing agent containing nano‐hydroxyapatite particles. By characterizing and reconstructing the transverse and longitudinal fracture in composite materials, the failure process of the composites under the action of stress was explained, and the interface theories of CF reinforced polymer were further explored. Highlights A kind of polyaryl ether ketone containing carboxyl functional group (PAEK‐COOH)was newly synthesized. HAp was distributed in the polymer sizing agent to obtain a HAp/PAEK‐COOH hybrid sizing agent. The interfacial adhesion of CF/PPEK composite was greatly improved by the hybrid sizing agent.